More on Blue Jays

Blue Jay, Cyanocitta cristata

Since Dan got his Master banding permit, we’ve put up a few nets to get a start on some of our planned projects. I mentioned the owl monitoring already in an earlier post. This morning we opened a net that we set up near our feeders. Dan goes into more detail on the purpose of the project, but essentially it’s to learn more about the local winter ecology of our resident birds – things like population sizes and demographics, survivorship over the winter, and general health of individuals (hopefully if we’re supplementing their diet with feed they’ll all be in good health, but it may lend some insight into the food resource abundance outside of the feeders).

There’s a lot of information that’s either extremely difficult or impossible to obtain without using banding studies. Two such pieces of info were evident from our efforts this morning. The first was that there were a lot more Blue Jays visiting our feeders than we’d first thought. By visual counts, simply watching the feeders and seeing who was around, we guessed there were perhaps 5 or 6 coming for seed. This morning, however, we caught no fewer than 8 separate individuals in the net, and later on, once we’d closed the net for the day, saw an additional 3 together at the feeder who had no bands, making a minimum of 11. We observed some of the banded individuals coming to the feeder again a short while later. Free food is hard to pass up! Evidently they weren’t too put off by the quick banding process.

The second thing we learned is that there’s an unusual proportion of adults to young birds among them. In an average fall, at an average banding location, one might expect to capture about 80-90% hatch-year (HY) birds – that is, birds that were hatched in this calendar year. The remaining 10-20% are after-hatch-years (AHY) – the adults who were parents this calendar year. Among our 8 Blue Jays captured this morning, a whopping 6 – 75% – were adults. This could mean either it was an exceptionally poor breeding year for Blue Jays in our woods and they didn’t raise many offspring, or the offspring have all dispersed or flown south, leaving just the adults to spend the winter here. It’s hard to know the reason for sure, although seeing what the proportions are come spring (after any migrants have presumably returned) will help to answer the question.

Blue Jay ages

You can tell the difference between the age classes of Blue Jays fairly easily. HY birds still have many of their “baby feathers”, that is, the set of feathers that they grew in while they were in the nest. They grow these feathers very quickly, because they want to limit the amount of time that they’re flightless and vulnerable to predation. However, because they grow them in all at once, and feathers are very energetically costly to grow, these “baby feathers” are of very poor quality. They’re generally rather coarse and dull, and will fade and wear down rapidly. Most songbird species have a pattern of moult whereby the HY birds will replace a portion of their feathers before the winter to see them through until their next moult (for some birds, this will be spring, but for many others they’ll have to wait until next fall). You can examine the feathers of a bird’s wing to see if it’s got any “baby feathers” – and most species have a very specific replacement pattern so it’s easy to know what to look for.

In the case of Blue Jays, the characteristic feathers are these small, outer feathers mid-way up the wing. They’re the little feathers that cover the sheathes of the long primary feathers (appropriately called the primary coverts), and the feather that comes from the thumb (the alula). In the above photo, you can see the left-hand bird, the AHY or adult, has very distinct barring to these outer feathers, and the colour is approximately the same as the larger neighbouring white-tipped feathers (the greater coverts, which cover the sheaths of the long inner secondary feathers). The right-hand bird, the HY or youngster, has relatively unmarked outer feathers which are a duller colour than the rich blues of the white-tipped greater coverts.

Blue Jay

I love Blue Jays’ wings, the blue colour in them is simply surreal. While most feather colours are created through various pigments, blue and green different. Like the sky, blue is created through the refraction of light, not the absorption of it. A red feather will still look red when lit from underneath, but a blue feather loses all of its colour – check out this page for some neat photos demonstrating this. Likewise, if you grind up a red feather, you have a pile of red dust, but grinding up a blue feather does not produce blue dust (it will more likely be brownish or grayish).

The exact light-scattering mechanism employed in these blue feathers has traditionally been assumed to be similar to what happens in the sky – the light hits the microscopic structures and then scatters in all directions, with just the blue coming back to your eye (so why don’t you see red or orange when viewed at a sharp angle, like sunsets, you ask? Good question, and I don’t know the answer.) A paper published in 1998 argued that the blue was created through a different scattering method, called interference or coherent scattering, whereby the light wavelengths break up and then come back together again, and the way they meet up again all the colours cancel themselves out except for the blue.

Whichever it is, the end result is that it’s a colour produced through structure, not pigment. And it’s pretty amazing. Can you believe so many people simply look past these guys, desensitized because they’re common?

Bold and bossy

Blue Jay, Cyanocitta cristata

When we first put the feeder up, the chickadees were the most common birds coming to visit, by virtue of the fact that they were the only ones who knew about it. Now that the word has spread, and we’re getting more species, the Blue Jays might be more frequent visitors. Undoubtedly, they’re the ones going through the most seed.

Blue Jays (Cyanocitta cristata) are real characters. They belong to the family Corvidae, which includes the jays and crows, generally felt to be one of the smartest groups of birds. For instance, jays often learn the call of the hawk species that inhabits their area, and then scream it out as they’re approaching a feeding station. At my parents’, they mimicked the Red-tailed Hawk; here, they do Red-shouldered Hawk. They’re pretty good mimics, and it’s usually enough to cause the birds already at the feeders to scatter, allowing the jays to have their pick of the food.

Blue Jay, Cyanocitta cristata

They’re also loud, vocal birds. Seeing a silent jay is much less common than seeing one that’s calling. In the fall and winter jays band together in loose groups, and their calls are partly used for communication between group members, keeping everyone together. Personally, I also think they just like to hear themselves talk. They have a wide variety of regular vocalizations, but their most common are the “jay” from when they take their name (although it could also be derived from an old German word, “gahi”, meaning “quick”), a “queedle-queedle” that sounds reminiscent of a squeaky closthesline, and various whistles.

Blue Jay, Cyanocitta cristata

And beyond even that, jays are gluttons. Or, at least, they get that reputation. Blue Jays have a pouch, or pocket, in their throats that they can tuck seeds in to, allowing them to pick up 10 to 15 at a time from a feeder. In the above photo this jay is throwing a seed back into one of the pouches. Usually when you see this behaviour it’s not because they’re greedy or especially hungry, but rather that they’re taking the seeds off to cache, or hide elsewhere. They use this behaviour to help ensure that they’ll have food to make it through the winter if heavy snows or prolonged weather prevents them from finding any at any time.

Blue Jay, Cyanocitta cristata

Jays aren’t the only birds that cache seeds from feeders, chickadees will also, and squirrels if they’re allowed to visit. In nature this behaviour would often apply to natural food sources such as acorns, and a single jay can cache up to 2000 to 4000 of them in a season. The jays only remember the locations of about 30% of their caches, using memorized landmarks to retrieve them, so inevitably some of the buried seeds will end up germinating. In the case of acorns, maples and other native species, this forgetfulness does the trees a favour in helping to get their seeds off to a good start.

Not all jays will cache seeds, depending partially on local food availability. The ones at my parents’ wouldn’t do it so much, but most of the ones here seem to. Or perhaps I’m just watching them more here. They’ll stuff their throat pouch till it’s bulging, and then take off to go hide them.

Blue Jay, Cyanocitta cristata

Although we tend to think of them as year-round residents, Blue Jays are actually a migratory species. Some will stick it out through the winter, but many hoof it south to more favourable climes, particularly in the most northern regions of their range. Blue Jays are found through virtually the entire east and Great Plains, and west through the Boreal forest, just nosing into northern BC. In the west their niche is filled by the Steller’s Jay (C. stelleri) a striking jay with an all-blue body and black head, and little blue (or white, depending on the subspecies) eyebrows. One of my favourite birds of my trips west have been these guys, both for their striking plumage and their character.

Migrating jays can be seen in flocks of anywhere from half a dozen to a few hundred. If you’re in a migrant-concentration area, such as a peninsula or a valley, you’ll often see jays flying high overhead in huge, silent groups in the fall. In a single morning in September it may be possible to see a few thousand go by overhead. These birds won’t go really far, just far enough for food to be easier to find come winter snow, a little like the juncos or some winter finches.

Blue Jay, Cyanocitta cristata

Although not a strict rule, larger birds generally live longer than smaller ones. Blue Jays have been recorded to live up to 18 years in captivity, though the chances of a wild bird even coming close to that age are fairly slim. Wild jays may live up to 6 years on average, usually succumbing to predation or weather pressures before they have a chance to experience old age. Various hawks, particularly the accipiters (Sharp-shinned, Cooper’s, and goshawk) are their main predators, being bird-specialists, extremely agile in woodland settings. The highest mortality rate occurs before the birds reach their first birthday, though, as they’re either helpless in the nest or still learning the ways of the world. This is why birds generally have such large clutches: most of the young won’t make it, even if they manage to raise them all to the point of leaving the nest.

Blue Jay, Cyanocitta cristata

Blue Jays are known for their bold behaviour. Falling in this category is mobbing. If you suddenly hear a big group of jays kicking up a fuss, shove your feet in your shoes and hurry out to see what it’s all about. Chances are there’s a hawk or an owl perched in a tree and the jays are expressing their displeasure, trying to encourage the bird to move on. Crows, weasels and foxes are also fair game, since they’re all potential predators of adults or their young. This mobbing behaviour is an adaptation that helps improve the survival of young (a predator that is driven off is one that isn’t eating your children). Although it seems like the adults are taking their life in their figurative hands, predators rarely try to attack them, usually because the birds are too quick for the predator to make a successful snap at one. Birds will usually mob in large groups, which also helps to protect individuals, since even if one was taken, the rest of the birds would continue dive-bombing the predator. I suspect mostly the predator just feels annoyed at being pinged on the head, and finds it easier to move on than try to catch one of these amazingly quick aggressors.

Blue Jay, Cyanocitta cristata

The jay, throat pouch full, crouches to take off for wherever he’s been hiding things. Jays really are very pretty birds, but overlooked because they’re so common. They’re entertaining to watch, even if they do go through our seed at an incredible rate, and they add a beautiful splash of blue to the feeder-scape. Hopefully as we get closer to winter they’ll get over their caching behaviour and just settle in to normal feeding (though they may carry on all winter).